You mean WMD stand for water, mostly deionised?
:-)
Brian
Douglas O. Pauls wrote:
> One would HOPE that the toast is lead-free. I might have concerns about MY
> long term reliability othewise.
>
> I agree with what you say, but the term "verifiable objective evidence" is
> such a wonderfully vague term. You and I could probably trade war stories
> for a few days on the scant data that passes for "objective evidence".
>
> Doug Pauls
>
>
>
>
> "Whittaker, Dewey
> (AZ75)" To: [log in to unmask]
> <Dewey.Whittaker@HON cc:
> EYWELL.COM> Subject: Re: [TN] Contamination on a SOT-23 component
> Sent by: TechNet
> <[log in to unmask]>
>
>
> 02/11/2004 08:03 AM
> Please respond to
> "TechNet E-Mail
> Forum."; Please
> respond to
> "Whittaker, Dewey
> (AZ75)"
>
>
>
>
>
>
> Doug,
> And if that toast is a multigrain construction in the Lead-Free forum,you
> could have long term reliability concerns.
> Some of the criteria we have for high reliability assemblies in a
> potentially No-Clean(or low residue) soldering process is clean and
> solderable parts/PWBs.Verifiable objective evidence of meeting these
> requirements must be maintained and made available upon request.
> Dewey
>
>
>>-----Original Message-----
>>From: Douglas O. Pauls [SMTP:[log in to unmask]]
>>Sent: Wednesday, February 11, 2004 6:33 AM
>>To: [log in to unmask]
>>Subject: Re: [TN] Contamination on a SOT-23 component
>>
>>Good morning Daan,
>>
>>Where did you ever get that idea? Must have been one of those mornings
>>before I had my Diet Dew(s).
>>
>>Residues on components or bare boards is always an issue. If the residue
>>on either is a purely surface residue, then it is less of a concern if
>>they
>>are going into a no-clean assembly operation. It is more of a concern,
>
> or
>
>>critical, in no-clean assembly because you have no way of addressing
>
> those
>
>>residues.
>>
>>If the components or boards have absorbed residues, you are toast. You
>>"might" be able to do rescue cleaning in mild cases, but most often not.
>>The laws of physics are not subject to repeal or negotiation.
>>
>>Doug Pauls
>>
>>
>>
>>
>>
>> "d. terstegge"
>>
>> <[log in to unmask] To:
>>[log in to unmask]
>>
>> SGROUP.COM> cc:
>>
>> Sent by: TechNet Subject: Re: [TN]
>>Contamination on a SOT-23 component
>> <[log in to unmask]>
>>
>>
>>
>>
>>
>> 02/11/2004 03:16 AM
>>
>> Please respond to
>>
>> "TechNet E-Mail Forum.";
>>
>> Please respond to "d.
>>
>> terstegge"
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>Hi Brian,
>>
>>I understood from earlier posting of you and others that the lack of
>>cleanliness of incoming components is considered a risk ONLY for
>>no-clean technology. Now Cheryl obviously has a problem with
>>contaminated parts in a process that does include cleaning. This makes
>>me wonder how (in general) the chances are that a cleaning process
>>designed mainly for cleaning flux residues from pcb assemblies will
>>clean the variety of contaminants present on incoming parts. Perhaps you
>>can comment on this ?
>>
>>Daan Terstegge
>>Thales Communications
>>Unclassified mail
>>Personal Website: http://www.smtinfo.net
>>
>>
>>>>>[log in to unmask] 02/11/04 08:56am >>>
>>
>>Amen! Lord Doug has hit it on the head.
>>
>>It may interest you (academically) to know that the erstwhile company
>>I
>>owned manufactured the Microcontaminometer 20 years ago, through to
>>1991. It was capable of measuring the ionic contamination on parts as
>>small as a single diode. It was not a popular instrument: I think we
>>probably sold less than 50 of the beasts. What we did find was that
>>many
>>components were hopelessly badly contaminated. There is a whole
>>chapter
>>in my book on this subject, with photos. One IC, which is shown,
>>measured at 12.4 µg/cm2 eq. NaCl and this is by no means exceptional.
>>
>>My experience in my former professional life was that component
>>manufacturers cared even less about cleanliness than they did about
>>solderability and I know no reason why this state of affairs should be
>>any different today.
>>
>>Brian
>>
>>Cheryl Tulkoff wrote:
>>
>>
>>>I've been working on a tough but challenging contamination problem.
>>
>>The
>>
>>>contamination causes electrical leakage fails on a precision test
>>>instrument. Ion chromatography analysis points to an incoming
>>
>>cleanliness
>>
>>>problem on a SOT-23 component. Elevated choride and sulfate levels
>>
>>were
>>
>>>found on the components (5x - 10x greater ug/in2 levels than
>>
>>anything
>>
>>>found elsewhere on the boards). High levels were found even on our
>>
>>"good"
>>
>>>boards.
>>>
>>>We are trying to work with our supplier to identify and fix the
>>
>>problem
>>
>>>long term but are looking for some short term fixes as well.
>>
>>Repeated
>>
>>>water washing of the boards (high pressure spray cleaning) improves
>>
>>the
>>
>>>situation but does not fix it. Alcohol scrubs in the area further
>>
>>improve
>>
>>>it but don't eliminate the problem entirely.
>>>
>>>We have a only a DI water wash process (no surfactant/saponifier
>>>capability).Does anyone have any board or component cleaning
>>>recommendations?
>>>
>>>Are there any parts makers out there willing to tell me a little
>>
>>more
>>
>>>about parts cleaning after the lead plating process?
>>>
>>>What tool(s) do part makers use to verify cleanliness of parts?
>>>
>>>I don't have a tool capable of measuring what was found on the part
>>
>>so I
>>
>>>don't know where to go.
>>>
>>>Thanks, Cheryl Tulkoff
>>>
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